Preparing chemical solutions for conditioning boiler water



Dec. 13, 1955 B. .1. CROSS PREPARING CHEMICAL. SOLUTIONS FORCONDITIONING BOILER WATER Filed Oct. 1, 1951 cHEMmAL lNJECTlON TANK Pump

CHE ucAL souu-nou Fig. I.

INJECTION INVENTOR Bertram J. Cross BY lailgfi United States PatentPREPARING CHEMICAL SOLUTIONS FOR CONDITIONING BOILER WATER Bertram J.Cross, Nyack, N. Y., assignor to Combustion Engineering, Inc., New York,N. Y., a corporation of Delaware Application October 1, 1951, Serial No.249,091

4 Claims. ((21. 122 s79 This invention relates to preparing chemicalsolutions for conditioning the water utilized in steam generatingboilers, and it has special reference to a novel method and improvedmeans for accomplishing such preparation.

When chemicals used for conditioning boiler water are introduced into aboiler, they are usually admixed with or dissolved in water, and theresulting solution is forced into the boiler by means of a pumpspecially designed for delivery in accurate quantities against theboiler pressure. The pump discharges the solution through a relativelysmall pipe into the steam generating boiler, as at the drum thereof.

In many industrial power plants where condensate is not available foradmixture with or for dissolving the chemicals prior to their deliveryinto the boiler, it is usual to use either local tap water or boilerfeed water to make up the solution. Such waters usually contain calcium,magnesium and other salts which react with the chemicals to formunsoluble products. These products collect within and foul the chemicalfeed pump and depositin the chemical feed lines to clog them. Even whencondensate has been used for admixture with the chemicals, similarclogging has occured because of the contaminating salts from condenserleakage that frequently are present in the condensate.

According to the invention I overcome the above mentioned objections offouling the chemical feed pumps and of clogging the feed pipes by usingwater from the boiler itself for making up solutions of the chemicals.Such boiler water, even if it contains a high concentration of dissolvedsolids, does not contain unreacted hardness, or is substantially freefrom ingredients forming precipitates when reacting with the chemicals.

Other objects and advantages of my invention will become apparent fromthe following description of an illustrative embodiment thereof whentaken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic view showing a steam generating boiler havingassociated chemical feed apparatus arranged in accordance with theinvention to draw water from the boiler for admixture with the waterconditioning chemicals.

In the drawing like numbers refer to like parts, and reference character1 designates a steam generator having an upper steam drum 2 and a lowerwater drum 3 interconnected by a bank of steam generating tubesv 4. Hotgases from a furnace or from a process (not shown) may flow across thebank of tubes in the direction shown by the arrow 5 giving up heat tothe tubes and the boiler water therein to generate steam.

In the steam generator feed water is supplied to the boiler drum 2through pipe 6 by a pump (not shown), and the generated steam collectedin drum 2 leaves the boiler via offtake pipe 7. Moreover, water is bledfrom the generator through a pipe 8 in controlled amounts by means ofblow off valve 9, thereby maintaining a desired concentration ofdissolved solids in the water within the generator.

Patented Dec. 13, 1955 Chemicals for conditioning the boiler water ineach generator 1 are first introduced into a solution tank 10 from achemical supply tank 11. These chemicals may be of the conventionalvariety customarily used to precipitate the scale-forming salts in theraw water fed into the boiler at 6 so that those salts form a dispersedsludge which can be removed with the boiler blow down through valve 9.Such chemicals may be delivered into solution tank 10 at a properlycontrolled rate in any suitable manner as by the aid of a device 12 thatfeeds into pipe 13; the feeder here illustrated at 12 being driven by amotor through reduction gearing 14.

Water for admixing or for dissolving the chemicals in the solution tank10 is delivered thereinto via pipe 15.

In the preferred arrangement disclosed, the aforementioned pipe 15receives boiler water from a pipe 17 which is connected to the outletport 18 of a hydraulic motor 19. Said hydraulic motor 19 has its inletport 20 connected to pipe 21 which conveys boiler water from the blowoff line 8 into which it is connected at point 21'. A cooler 16 isserially connected into line 21 and cools the withdrawn boiler waterprior to its entry into the hydraulic motor 19.

The pump 22 removes the chemical solution from solution tank 10 via pipe23 and delivers it via pipe 24 into the steam generator 1.

The hydraulic motor 19 is directly connected through shaft 30 to thecentrifugal pump 22. This motor 19 is driven by boiler water underpressure supplied through pipe 21 from blow oh line 8. The boiler waterwhich is exhausted from the motor 19 at outlet 18 flows at a reducedpressure through pipes 17 and 15 to the solution tank 10. A control,such as a float control valve 31, may be connected in line 15 toregulate the flow of water into the solution tank 10. Since thehydraulic motor 19 must use more water than is needed by the solutiontank 10 in order to pump the water leaving tank 16 back into the boilerand overcome the power loss inherent in the pumping system, the excesswater is carried ofl through pipe 32 into the blow off line 8 beyond theblow off valve 9 and into the flash tank 33 and thence to waste; a checkvalve 34 being shown in pipe 32. In order to provide a reasonableoperating head for forcing water through line 15 and valve 31 into tank10 the pipe 32 is extended a distance above the tank and then extendeddownward to checkvalve 34.

Should it be desired to reduce the pressure of the water supply to pump19 an adjustable pressure reducing valve 38 may be provided in the lineleading to this pump.

As mentioned above, the boiler water withdrawn from blow-off line 8 inthe manner here taught does not contain unreacted hardness, or issubstantially free from ingredients forming precipitates when reactingwith the chemicals. Therefore when such boiler water is employed as thesolvent in chemical solution tank 10 there is no fouling of the chemicalfeed pump 22' or clogging of the chemical feed pipes 2324 by the make upsolution as it flows therethrough into the steam generating boiler.-

There isanother advantage accruing from the use of boiler water inthechemical solution when acid salts such as monosodium phosphate areemployed as the chemical. This salt is highly corrosive and will attackthe material of the pumps 22--22', the hydraulic motor 19, and the pipelines 23-24. My herein-disclosed use of the alkaline boiler water as asolvent will lower if not completely neutralize the acidity of this andsimilar salts.

While I have here shown and described illustrative apparatus forpracticing my invention, it will be understood that changes inconstruction, combination, and arrangement of parts maybe made Withoutdeparting from the spirit and scope of the invention as claimed.

What I claim is:

1. In a steam generating boiler, the combination of a chemical feed pipeconnected to said boiler; a vpump connected at its discharge end to saidfeed ,pipe for delivery of chemical into said boiler; a hydraulic :motorcoupled with said pump to drive it; a first ,pipc leading from saidboiler to the inlet of said motor for the delivery of boiler water underpressure into the motor; .a solution tank for admixture ofchemical andwater; a'second pipe leading from the outlet of said motor into saidsolution tank, whereby water from the boiler carried to the motor bysaid first pipe serves to drive said motor and thereby said pump andwhereby said motorin thus beingdriven serves to reduce the pressure ofsaid boiler water flowing therefrom via said second pipe into said tank;conduit means connecting said solution tank to the inlet of said pump;and means to supply chemical to said solution tank for admixture thereinwith the'aforesaid boiler water reaching the tank via said second pipe,said chemicals being eifective to condition the boiler water byprecipitating the scale forming salts in the raw water fed to the boilerbut being non-reactive with previously conditioned boiler water.

2. In a steam generating boiler, the combination of a chemical feed pipeconnected to said boiler; a pump connected at its discharge end to saidfeed pipe for delivery of chemical into said boiler; a hydraulic motorcoupled with said pump to drive it; a first pipe leading from saidboiled to the inlet of said motor for delivery of boiler water underpressure into the motor; a solution tank for admixture of chemical andwater, said tank communicating with the inlet of said pump; a secondpipe leading from the outlet of said motor into said solution tank,whereby water from the boiler carried to the motor by said first pipeserves to drive said motor and thereby said pump and whereby said motorin thus being driven serves to reduce the pressure of said boiler waterflowing therefrom via said secondpipe into said tank; means to supplychemical to said solution tank for admixture therein with the aforesaidboiler water reaching the tank via said second pipe, said chemicalsbeing effective to condition the boiler water by precipitating the scaleforming salts in the raw water fed to the boiler but being non-reactivewith previously conditioned boiler water; valve means in said secondpipe responsive to the amount of solution in said tank for controllingthe aforesaid flow of boiler water into the tank; and means alsocommunicating with said second pipe for carrying away from saidhydraulic motor allboiler water discharged therefrom that is preventedby said valve means from entering said solution tank.

3. In a steam generating boiler, the combination of a chemical feed pipeconnected to said boiler; a pump connected at its discharge end 'tosaidfeed pipe for'delivery of chemical into said boilerya hydraulic motorcoupled with said pump to drive it; a first pipe leading from saidboiler to the inlet of said motor fordelivery of boiler water underpressure into the'motor; a'solution tank for admixture ofchemical'and-water, said tank communicating with the inlet of said pump;a secondpipe leading .from the outlet of said 'motorinto'said solutiontank, whereby water from the "boiler carried to the motor by said firstpipe serves to drive said motor and thereby said pump and whereby saidmotor in thus being driven serves to reduce the pressure of said boilerwater flowing therefrom via said second pipe into said tank; means tosupply chemical to said solution tank for admixture therein with theaforesaid boiler water reaching the tank via saidsecond pipe, saidchemicals being efiective to condition the boiler water by precipitatingthe scale forming salts in the raw water fed to the boiler but .beingnon-reactive with previously conditioned boiler water; a blow down lineconnected to said boiler; a blow oif valve in said blow down line; athird pipe disposed to carry boiler water leaving said motor and notreceivable by said tank from said second pipe into said blow down linebeyond said blow off valve with respect to water fiow there through; anda check valve disposed in said third pipe to permit water flowtherethrough only in the direction of towards said blow down line.

4. In a steam generating boiler, the combination of .a chemical feedpipe connected to said boiler; a pump connected at its discharge end tosaid feed pipe for delivery of chemical into said boiler; a hydraulicmotor coupled with said pump to drive it; a first pipe leading from saidboiler to the inlet of said motor for delivery of boiler waterunderpressure into the motorya solution tank for admixture of chemicaland water, said tank communicating with the inlet of said pump; a secondpipe leading from the outlet of said motor into said solution tank,whereby water from the boiler carried to the motor by said first pipeserves to drive said motor and thereby said pump and whereby said motorin thus being driven serves to reduce the pressure of said boiler waterflowing therefrom viavsaid second pipe into said tank; means to supplychemical to said solution tank for admixture therein with the aforesaidboiler water reaching the tank via said second ;pipe, said chemicalsbeing efiective to conditionthe'boiler water by precipitating the scaleforming salts vin the raw water fed to the boiler but beingtnon-reactivewith previously conditioned boiler water; a third pipe communicatingwith said second pipe and extending upwardly therefrom to atlevel abovesaid tank before leading to apoint of discharge; and valve meansintermediate said second vpipe and tank responsive to the amount ofsolution'in said tank for controlling the aforesaid flow of boiler waterinto the tank whereby boiler water discharging from said hydraulicmotortfiows into said tank as longas said valve means permit and whenrejected by the tank passes upwardly into'and through said thirdpipe.

References Cited in the file of this patent UNITED STATES PATENTS825,971 Hutchison July 17, 1906 1,255,170 'Jacobus -Feb. 5, 19181,314,140 "Iacobus Aug. "26, 1919 1,341,213 'Jacobus May 25, 19201,442,274 Jacobus Jan. 16, 1923 1,774,211 Piccardo Aug. 26, 19302,151,297 Lucke Mar. 21, 1939 2,226,592 Stern Dec. 31, 1940 2,312,570'Meier Mar. 2, 1943

